A transformer coil has a coil tube, which is surrounded by a secondary winding and a primary winding, the latter of which is embedded in a block of insulating material, the windings being produced by the so-called filament winding method. For this purpose, a first insulating layer is wound onto the coil tube, which is separated from the secondary winding by means of spacers, and a first layer of the winding wire is wound onto said first insulating layer. A layer of insulating material is applied to this first wire layer, again a layer with winding wire is applied to this insulating layer, this wire layer comprising two layer sections, which extend inwardly, i.e. toward one another, from the two ends of the inner layer of the winding wire and end at a certain distance from one another. The opposite ends of the inner layer are connected to the adjacent ends of the second layer sections. In the case of known winding methods, it must be ensured here that the opposite ends of the second layer sections do not slip off outward over the inner first layer. This is achieved by the opposite winding ends of the second layer sections being at an axial distance from the winding ends of the inner layer, so that the connections of the adjacent winding ends each form an acute angle with the annular surface of the inner first layer; the two angles together form a V shape, the open side of which is open toward the inner first layer.
The mutually opposing ends of the second layer sections are each adjoined by a third layer section, with an intermediate layer of insulating material in turn being introduced between the second and third layer sections. The mutually opposing ends of the third layer sections end again at a distance from the adjacent ends of the second layer sections, so that the connections of the inner, mutually opposing ends of the second and third layer sections likewise together form an acute angle, with the two connections forming a V shape, the tip of which points radially inward. These three layer sections are followed, for example, by two fourth and fifth layer sections, the lengths of which are axially shortened with respect to the previously wound layers, so that here too the V shapes are formed.
These winding forms, i.e. the offset, have the result that the winding space available is not optimally and fully utilized.